1. Field of the Invention
The present invention relates to a data migration system for a storage system, that does not need to stop I/O access from a host computer when migrating data from a first storage subsystem to a second storage subsystem and switching the connection destination of the host computer from the first storage subsystem to the second storage subsystem.
2. Description of Related Art
In storage systems, in order to replace a first storage subsystem, to which a host computer is currently connected, with a second storage subsystem, data stored in the first storage subsystem volumes is copied to the second storage subsystem.
The method for migration between storage subsystems disclosed in Japanese Patent Laid-open Publication No. H11-184641 is known as a migration method that does not stop read/write (I/O) access from the host computer during the above copying process.
More specifically, according to the above method, a plurality of first access paths is provided between a CPU and an old subsystem; a plurality of second access paths is provided between the CPU and a new subsystem; and a plurality of third access paths is provided between the old and new subsystems. The connection destination is changed from the old (migration source) subsystem to the new (migration destination) subsystem by switching the first access paths to the second access paths over several cycles. If the new subsystem is accessed by the CPU via the second access paths provided on the new subsystem's side while the connection destination is being changed, a path migration controller provided in the new subsystem handles that access by transferring it to the old subsystem via the third access paths. After all first access paths have been switched to the second access paths, data migration is performed from the old subsystem to the new subsystem.
In the above prior art method, paths are created between a migration source storage subsystem and a migration destination storage subsystem, and using the paths, a host computer accessing the migration destination storage subsystem can access a migration source volume in the migration source storage subsystem.